Patch "netvsc: add rcu_read locking to netvsc callback" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

netvsc: add rcu_read locking to netvsc callback

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
netvsc-add-rcu_read-locking-to-netvsc-callback.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: stephen hemminger <[email protected]>
Date: Wed, 11 Jan 2017 09:16:32 -0800
Subject: netvsc: add rcu_read locking to netvsc callback

From: stephen hemminger <[email protected]>

[ Upstream commit 0719e72ccb801829a3d735d187ca8417f0930459 ]

The receive callback (in tasklet context) is using RCU to get reference to associated VF network device but this is not safe. RCU read lock needs to be held. Found by running with full lockdep debugging enabled.

---
 drivers/net/hyperv/netvsc_drv.c |    3 +++
 1 file changed, 3 insertions(+)

@@ -659,6 +659,7 @@ int netvsc_recv_callback(struct hv_devic
 	 * policy filters on the host). Deliver these via the VF
 	 * interface in the guest.
 	 */
+	rcu_read_lock();
 	vf_netdev = rcu_dereference(net_device_ctx->vf_netdev);
 	if (vf_netdev && (vf_netdev->flags & IFF_UP))
 		net = vf_netdev;

@@ -667,6 +668,7 @@ int netvsc_recv_callback(struct hv_devic
 	skb = netvsc_alloc_recv_skb(net, packet, csum_info, *data, vlan_tci);
 	if (unlikely(!skb)) {
 		++net->stats.rx_dropped;
+		rcu_read_unlock();
 		return NVSP_STAT_FAIL;
 	}
 

@@ -696,6 +698,7 @@ int netvsc_recv_callback(struct hv_devic
 	 * TODO - use NAPI?
 	 */
 	netif_rx(skb);
+	rcu_read_unlock();
 
 	return 0;
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/netvsc-add-rcu_read-locking-to-netvsc-callback.patch